Air damper assembly including sidewall sealing means



F. T. M CABE May 7, 1968 AIR DAMPER ASSEMBLY INCLUDING SIDEWALL SEALING MEANS 5 Sheets-Sheet 1 Filed Aug. 29, 1966 z's TKZ ZZMB i 'zarcc May 7, 1968 F, 'T, M CABE 3,381,601

AIR DAMPER ASSEMBLY INCLUDING SIDEWALL SEALING MEANS Filed Aug. 29, 1966 s Sheets-Sheet 2 "*Illlm.

y 7, 1968 F. T. MCCABE 3,381,601

AIR DAMPER ASSEMBLY INCLUDING SIDEWALL SEALING MEANS Filed Aug. 29. 1966 5 Sheets-Sheet 5 F. T. M CABE May 7, 1968 AIR DAMPER ASSEMBLY INCLUDING SIDEWALL SEALING MEANS 5 Sheets-Sheet 4 Filed Aug. 29, 1966 y 1968 F. T. MOCABE 3,381,601

AIR DAMPER ASSEMBLY INCLUDING SIDEWALL SEALING MEANS Filed Aug. 29. 1966 5 Sheets-Sheet 5 4 'g w'z Z66 Z60 a Z45 6 IIIIIIII/ Jrzz/e rzzc zarzc zs TZZ CaAe United States Patent 3,381,601 AIR DAMPER ASSEMBLY INCLUDING SIDEWALL SEALING MEANS Francis T. McCabe, Cook County, Ill., assignor to M & T Engineering Company Filed Aug. 29, 1966, Ser. No. 575,745 16 Claims. (Cl. 98-121) The present invention relates to an air damper and more particularly to an air damper having a novel blade and pivot construction yielding a highly effective seal between adjacent blades and the housing and blades.

Designers of prior art air dampers have long sought to provide a device in which the blades may be easily moved to an open position to allow unimpeded air flow through the device while creating an effective air seal when the blades are closed. Such construction additionally requires that the blades, pivot means and linkage for connecting the blades be mechanically simple so as to be relatively free of maintenance and inexpensive to manufacture and fabricate.

One type of air damper which the prior art fails to satisfactorily disclose with reference to the above-mentioned problems is a damper which allows air flow in one direction only, commonly referred to as a backdraft damper. This device is adapted to allow air to pass from the interior of a building to the environment while precluding wind, backdraft, rain, dust, smoke or obnoxious fumes from entering through the damper. Backdraft dampers may be operated by the differential pressure across the damper or by manual or automated control devices. To perform effectively, such dampers must have eflicient seals to prevent the passage of air, in the wrong direction, between the blades and between the blades and the housing. The prior art, however, has failed to provide a backdraft damper which provides an efficient seal in combination with off-end pivot means. Furthermore, some devices are unuseable in both .a vertical (wall) or horizontal (ceiling) application without springs or bias ing to assure closure of the blades.

Backdraft dampers should also be constructed so that the blades are relatively balanced about the pivot axis whereby in a vertical installation the blades will normally, i.e. without significant pressure differential, rest in a closed position. Prior art devices have attempted to solve this requirement by providing the blades with properly positioned counter-balances, but such construction increases material and fabrication costs.

Another type of air damper which the prior art fails to satisfactorily disclose is an off-end blade pivot air-control damper, which allows a selected volume of air to pass through the damper in either direction, while maintaining an effective seal in the closed position. These devices are generally controlled manually or automatically to set the blades in a particular position which governs the air passage therethrough. Again the problem left unsolved in the prior art air-control dampers is the effective sealing between the adjacent blades and the blades and housing.

Accordingly, it is one object of this invention to provide an air damper having blade, pivot means and frame or housing construction so that the adjacent blades and the blade ends and housing have an effective seal for preventing the passage of air when the blades are in a closed position without the addition of separate blade sealing means attached to the blade ends to effect the seal between the blades and housing.

Another object of this invention is to provide an air damper having a blade assembly wherein individual blade side edge portions overlap the frame side members to form a seal and the longitudinal edges of the blades are in sealing engagement with one another and with the top and bottom frame members to form a seal when the blade assembly is in a closed position and each of the blades are independently supported by the frame.

'Still another object of the present invention is to provide an air damper of the above-described type in which each blade of the blade assembly is fixedly and securely mounted to the frame without any brackets, attachments or appendages secured on the blade.

Yet another object of the present invention is to provide an air damper of the above-described type in which the blades are connected by a linkage which provides an automatic opening stop for the blades without additional appendages mounted on the blade.

One more object of the present invention is to provide an air damper of the above-described type having a blade and housing construction so that adjacent blades may be simultaneously opened in the same or opposite direction by suitable linkage means and blade mounting.

For a better understanding of the invention together with other further objects thereof, reference should now be made to the following detailed description which is to be read in conjunction with the accompanying drawings in which:

FIGURE 1 isa perspective view of a backdraft air damper constructed in accordance with the present invention;

FIGURE 2 is a top plan sectional view of the air damper illustrated in FIGURE 1 taken along the line 22;

FIGURE 3 is a side elevation sectional view of the air damper illustrated in FIGURE 1 shown in the closed position;

FIGURE 4 is aside elevation sectional view of the air damper illustrated in FIGURE 1 shown in the open position;

FIGURE 5 is a detailed front elevation view of the blade pivot means and blade linkage means;

FIGURE 6 is an exploded perspective view of the blade pivot means;

'FIGURE 7 is a side elevation detailed sectional view of the blade pivot means;

FIGURE 8 is a top plan partial sectional view of the blade and linkage means connection shown with the blade in a closed position;

FIGURE 9 is a side elevation partial sectional view of the blade and linkage means connection shown with the blade in an open position;

FIGURE 10 is a top plan partial sectional view of the blade and linkage means alternate connecti'on shown with the blade in a closed position; 1

FIGURE 11 is a detailed sectional side elevation view of the blade gasket;

FIGURE 12 is a detailed sectional side elevation view of one blade g'aske't engaging the adjacent blade;

FIGURE 13 is a side elevation sectional view of one control means for the blade assembly;

FIGURE 14 is a side elevation sectional view of a second control means for the blade assembly;

FIGURE 15 is a side elevation sectional view of a third control means for the blade assembly;

FIGURE 16 is a side elevation sectional view of an air control damper blade assembly constructed in accordance with the present invention, shown in a closed position;

FIGURE 17 is a side elevation sectional view of the blade assembly illustrated in FIGURE 16, shown in the open position;

FIGURE 18 is a partial front elevation view of a blade mounting assembly; and

FIGURE 19 is .a side elevation sectional view of an alternate mounting of the blade assembly illustrated in FIGURES 16 and 17 shown in the closed position in full lines and in the open position in phantom lines.

Briefly stated, the invention provides an air damper comprising a frame or housing and a blade assembly including a plurality of individual blades independently pivotally mounted on the side members of the frame, eaoh blade having a length so that the side edge portions overlap the frame side members forming a seal and the longitudinal edges of the blades are in sealing engagement with one another and with the top and bottom frame members forming a seal. The blades are characterized by an offset section intermediate the longitudinal edges having a center line co-axial with the blade pivot axis so that the upper and lower blade sections owerlap the frame side members on opposite sides thereof. The blades are further characterized by a cross-sectional shape for direct secure engagement (with a slotted pivot shaft. Lin'k'age means is provided for simultaneous opening and closing of the blades and adjacent blades may be mounted for opening in the same or opposite directions in conjunction with suitable linkage means.

Referring now to FIGURES 1 through 4, there is shown one embodiment of 'an air damper indicated generally with the reference numeral 30. Air damper is a backdraft damper comprising a frame or housing 32 and a blade assembly 34. Housing 32 comp-rises four aluminum extruded members 36, 38, and 42 and is constructed with miter joints. The housing shown has a front flange 44 (front being indicated by the forward direction of air flow as shown by the arrow on FIGURE 1) for mounting on the interior surface of a wall. The housing may be constructed with a back flange for exterior surface wall mounting or without any flange so as to be entirely c n-' tained Within the Wall, ceiling, air duct or the like.

The top and bottom frame members 36 and 38 respectively have an identical E-sh'ape eross--section, as shown best in FIGURES 3 and 4, and are arranged as mirror images in the frame. Since each member is the same in cross-sectional shape, differing only in its position in the assembled frame, the components forming each member are given like reference numerals. That is, each member comprises an inwardly directed front, center and rear leg designated by '44, 46 and 48, respectively. Center legs 46 form the top and bottom shelf which is in sealing contact with the blade assembly when the damper is in a closed position.

Opposed frame side members 40 and 42 also have the identical E-shape cross-section, as shown best in FIG- URE 2, and are likewise arranged as mirror images in the assembled frame. Since each member has the same crossse'ctional shape, differing only in its orientation, the components forming each frame side member are given like reference numerals. Each member comprises inwardly directed front, center and rear legs designated by numerals 50, 52 and 54, respectively. Front and rear legs, and 54, have a longitudinally extending fastener boss integralily formed on the facing surfaces and adapted for receiving a screw or similar fastener. Upper and lower frame members 36 and 38 have suitably provided holes in registry with the fastener bosses when the frame is assembled and secured by screws.

Center legs or side member shelves 52, as seen best in FIGURE 5, have a plurality of notches 58 adapted for receiving a bearing which is part of the pivot means for supporting the individual blades of the blade assembly 34 as more fully described hereinafter. Center legs 52 of frame side members 40 and 42, together with center legs 46 of top and bottom frame members 36 and 38 form a rectangular sealing shelf 60 which is in contact with the blade edges of the blade assembly when the damper is in a closed position.

Blade assembly 34, in the air damper as illustrated in FIGURES 3, 4 and 5, comprises three longitudinally extending blades designated from top to bottom as 62, 64 and 66. Each blade is independently supported by the side frame members through pivot means 68 connected to each blade at opposite ends. The blade pivotal axis is located approximately one-fifth of the width of the blade as "measured from the upper longitudinal edge. Each blade is identical and description of one such blade will be sufficient.

Blade 66 comprises a fiat lower section 70, an upper section 72 and an offset section 74. The center line of the offset section 74 is coaxial with the pivotal axis of the blade and has a lateral Width equal to the thickness of the frame member rectangular sealing shelf 60. As seen in FIGURE 5, the side edge portion 76 of blade 66 extends or overlaps the edge of frame side member shelf 52. The upper section side portion 78 overlaps shelf 52 above notch 58 so as to be in contact with one surface of shelf 52. Similarly, the lower section side edge portion 80 overlaps shelf 52 below notch 58 so as to be in contact with the opposite surface of shelf 52.

It will therefore be seen that by offsetting the blade at the pivotal axis the upper and lower blade section edge portions of each blade will be in contact with the opposite surfaces of the shelf and form a seal along the almost complete width of the blade. Rather minute gaps 82 appear on each side of pivot means 68 but these may be blocked by forming a cylindrical flange on the pivot means blade shaft between the edge of the blade and the pivot means hearing, as more fully described hereinafter.

The blades 62, 64 and 66 are interconnected so as to open and close in unison by linkage means 84 which comprises a linkage bar 86 connected to the upper or leading edge of each blade by pins 88. The bar has a series of notches 90 so as to provide clearance between the pivot means 68 and the edge of linkage bar 86. As seen best in FIGURE 1, linkage means 84 is entirely confined within frame 32 and is thereby assured freedom of operation without being obstructed.

Moreover, linkage means 84 cooperates with each blade so as to provide an automatic stop position for the opening of the blades, as seen in FIGURES 5, 8 and 9. The upper or leading edge of blade 66 includes a scroll or circular are 92 offset from the plane of the blade upper section 72 which is adapted to receive pin 88 with a snug fit. A notch 94 is transversely cut near one end of the blade from the top of the blade through the circular are 92 and a short distance therebelow ending with stop surface 96. Linkage bar 86 is positioned in slot 94 and connected by inserting pin 88 through circular are 92 and a hole in linkage bar 86. As seen in FIGURE 9, when blade 66 pivots into the open position it will continue to swing upward until notch stop surface 96 contacts the edge of linkage bar 86 preventing further opening of the blade.

An alternate embodiment for connecting the linkage bar 86 to the blade 66 is shown in FIGURE 10. The linkage bar 86 is attached to the side edge of blade 66 by a pin 98 having a shaft 100 protruding into the blade circular are 92, a bearing surface 102 for insertion into a hole in linkage bar 86, and a head 104 for retaining the bar 86 on bearing surface 102. No blade stopping means is provided by this connection.

It will be noted that pins 88 and 98 have a length which will prevent their movement out of circular are 92 irrespective of how loose the pins fit in the circular arc. Should the pins begin to work out of the circular are 92, the end of the pin will butt against frame member 42 and will be prevented from complete disengagement with circular are 92 and linkage bar 86.

Pivot means 68 for supporting a blade is shown in FIGURE 6 as comprising a bearing 106 and a shaft 108. Bearing 106 is provided with a slot 110 extending on opposite sides and across the rear face of bearing 106 and fits snugly into notch 58 in frame side member shelf 52. An opening 112 is provided in the front face of bearing 106 for receving journal 114 of shaft 108. Journal 114 is, of course, cylindrical and the shaft then tapers into a hexagonal portion 116 having an irregularly shaped slot 118 for receiving the blade.

As seen best in FIGURE 7, the hexagonal portion 116 is bifurcated into two blade gripping members 120 and 120a. Both gripping members are identical and arranged as inverted mirror images of one another and the like parts of each member are designated by the same numeral. Each gripping member comprises two fingers 124 and 126 and a thumb 128 which is shorter than the fingers. An indentation 130 is formed between fingers 124 and 126 and a second indentation 132 between finger 126 and thumb 128.

It will be appreciated that each finger and thumb of one gripping member is positioned opposite an indentation of the other member. For example, thumb 128 is opposite indentation 130a, finger 126 is opposite indentation 132a and finger 124 is positioned outside of gripping member 120a.

Consider now the cooperation of gripping members 120 and 120a with blade 66. As previously indicated, shaft 108 engages blade 66 at the pivotal axis thereof, ie. the offset section 74. The edge of blade 66 is forced into slot 118" of shaft 108 so that the fingers 126 and 126a bear against the arcuate portions 134 and 136 of blade 66, respectively. This prevents the blade from moving transversely relative to the shaft. The blade is also laterally restrained from movement relative to the shaft since fingers and thumb bear against the blade opposite the indentations. Since each finger is opposite an indentation, however, stresses are not created in the gripping members as would occur if the fingers were opposed on each side of the blade.

The irregular slot in the shaft 108, therefore, will be seen to be particularly adapted for supporting thin metal blades. The assembly of the blade and shaft is extremely simple involving no fasteners or welding and the blade itself does not support any bearing attached thereto. The shaft 108 and bearing 106 are preferably made of a plastic material and it is therefore important to eliminate as much stress as possible from the shaft to maintain service life. Such stress relief is provided by the novel shaft gripping member configuration wherein the opposing fingers do not bear directly against one another. Furthermore, the shaft-blade connection is extremely resistant to loosening due to vibration and unlike prior art bladeshaft connections actually tightens if the blade portion in engagement with the shaft is deformed.

Referring now to FIGURE 11, it will be seen that the lower end of each blade has a channel 138 for receiving a feather-edge gasket 140. Channel 138 is formed with a trapezoidal cross-section. Gasket 140 is formed of rubber or plastic and has a longitudinally extending trapezoidal cross-section base 142 with a lateral projecting portion 144 and a feather-edge contact portion 146 projecting transversely. The contact portion 146 protrudes laterally from the blade a distance slightly exceeding the thickness of the frame side member shelf 52.

'As seen in FIGURE 12, the upper section 72 of blade 66 has an inset portion 148 for receiving the tip of feather-edge portion 146 of gasket 140 so as to form a seal between adg'a'cent blades. It will be appreciated that an increase of back pressure against the blade assembly will produce .a tighter seal since the gasket 140 will deflect, increasing contact with the blade inset 148.

The gasket 1 40 is easily engaged with blade channel 138 by simply sliding the gasket in the channel where it is maintained in frictional engagement. As seen in FIGURE 5, the length of gasket 140 is slightly less than the length of the blade so as to permit the blade upper and lower section side edge portions 78 and 80 to contact frame side member shelf 52 in sealing relation.

As seen best in FIGURE 3, the blade assembly 34 is sealed to frame 32, at the top and bottom as well as along the side edges of the blades. The uppermost blade upper sect-ion 72, above the inset 148, contacts the lower edge of the frame top member shelf 46 forming a seal which is made increasingly effective by a rise in back pressure which compresses gasket 140. The lowermost blade is also in sealing contact with frame bottom member shelf 46 by removing g'asket from channel 138 allowing the lower edge and side edges to contact the bottom and side shelves. The height of the entire blade assembly 34 may be adjusted to a frame of any height by simply removing the required lower portion of the lowermost blade without affecting the lower sealing relation.

Various control means of the individual blades of the air dam per blade assembly may be used to open and close the air flow opening. In many installations, there will be no control means used to open and close the damper blades. The backdraft damper is designed so that the pivotal axis of each blade is positioned sufficiently close to the upper longitudinal edge of the blade so that the blade portion below the axis is slightly heavier than the upper portion of the blade and the linkage means. In this manner, the blade assembly will be normally closed regardless of whether the air damper is mounted vertically or horizontally. The blade sealing gasket will contact, or nearly contact the inset portion of the adjacent lower blade. A tight seal is obtained by the backdraft pressure which will force each blade gasket against the adjacent blade inset portion. Of course, opening of the blades occurs by the pressure of air flow through the damper on the lower portion of the blade which is considerably greater in area than the portion of the blade above the pivotal axis and consequently develops a force to rotate the blades upwardly.

In the event that the air damper installation requires positive control means for opening and closing the blade assembly, manual or motor-controlled operation may be provided. In this regard, attention is directed to FIG- URES 13 through 15 showing various control means.

FIGURE 13 shows a frame side member having a shelf 162 supporting pivot means 164 and blade 166. The remaining blades of the blade assembly will be understood as moving simultaneously with blade 166 through linkage means 168. A motor bracket 170 is mounted at the rear of frame side member 160 and supports a stalling motor 172 having a control arm 174 fixedly mounted at one end on mot-or output shaft 176. A blade control arm 178 is fixedly mounted at one end of blade shaft 180 of pivot means 164. A connecting arm 182 pivotailly interconnects the free ends of motor control arm 174 and blade control arm 178. In operation, activation of motor 172 will rotate blade 166 and the connected bla'des to the full open position at which time motor 172 will stall maintaining the blade in the open position until the motor is activated in a reverse direction so as to close the blade assembly. A single dire'ction motor may also be used by resiliently biasing the blade to a closed position whereby u'pon de-activa-tion of the motor the resilient force will close the blade assembly.

FIGURES 14 and 15 show manually controlled blade assemblies in which like parts are indicated with like reference numerals. Referring first to FIGURE 14, there is shown a frame side member 180 having a shelf 182 for supporting pivot means 184 on which is mounted blade 186. The air damper blade assembly includes a plurality of blades identical to blade 186 which are interconnected by linkage means 188. A blade control arm 190 is fixedly secured to a blade shaft 192. A control arm clamping bracket 194 is secured at the re'ar of frame side member 180 having an arcuate slot 196. A locking means 198 is mounted on control arm 190 and cooperates with slot 196 to position blade 186 in any position from fully closed to fully open by unloosen'ing a lock-ing nut rear portion of frame side member 180 which supports a pulley 204 on a shaft 206. A chain 208 is secured to the free end of control arm 190 and passes under pulley 204. The free end of chain 208 may be secured to a wall or ceiling bracket (not shown), having a bayonet slot or the like, to secure and maintain control arm 190 in the desired position. Control arm 190 may be spring biased to an open or closed position if desired.

Referring now to FIGURES 16 through 19, there is shown an air control damper constructed in accordance with the present invention. The frame construction for the air control damper is substantially similar to that of the backdraft damper in that the cross-sectional shape of the to'p, bottom and side members is generally the same. However, air control damper applications require that stee'l rather than aluminum material be used and thus the frame members are not extruded but are fabricated by other methods well known in the art. The frame side member is indicated by the reference numeral 220 and the frame side member shelf by numeral 222.

The blade assembly 224 com'prises a plurality of blades, two of which are shown and designated by reference nu rnerals 2'26 and 228 in FIGURES 16 through 18. This embodiment of the novel air control damper is generally referred to as a parallel opening air damper by virtue of the linkage means employed to simultaneously open and close the plurality of blades. Since each blade is identical, it will suffice to describe only one of such blades.

Blade 226 has a lower section 230, an upper section 232 and an offset section 234. The axis of rotation of the blade is coaxial with the center line of the offset section 234 and the area of the upper and lower blade sections are substantially equal. The length of blade 226 is greater than the opening between opposed frameside member shelves 222 so that the blade upper section side edge portion 236 will overlap the edge of shelf 222 contacting one surface thereof and the blade lower section side edge portion 238 will overlap the shelf edge contacting the opposite surface thereof. The longitudinal edges of the upper and lower blade sections include a longitudinally extending channel 240 for receiving a gasket 242. Channel 240 is formed with a trapezoidal cross-section with arms 244 and 246 extending inwardly toward one another and base 248 positioned parallel to the plane of blade lower portion 230. Gasket 242 has a trapezoidal base 250 and a fish tail shaped cross-sectional contact portion 252 which projects laterally from the blade plane and then transversely parallel thereto. As will be seen in FIGURE 16, the fish tail shaped portions 252 of adjacent blades overlap along their curved parallel edges forming a seal between adjacent blades.

Pivot means 254 are fixedly mounted in each oppositely disposed frame side member shelf 222 for supporting blade 226. Pivot means 254 comprises a bearing 256 for receiving a blade shaft journal 258 having a slot 260 for receiving the side edge of the blade. Blade offset section 234 includes a laterally disposed flat segment 262 which is in firm engagement with slot 260 and armate segments 264 and 266 which engage the outer surface of journal 258. A cylindrical flange 268 is integral with journal 258 and positioned between the edge of blade 226 and the face of bearings 256 to substantially close the gap between the blade edge and bearing. Alternatively, journal 258 may have a diameter substantially equal to the diameter of flange 268 and a lesser diameter journal portion received in bearing 256.

Parallel linkage means 270 comprises linkage bar 272 pivotally connected to an arm 274 fixedly mounted on the blade lower section 230 of each blade. As seen best in FIGURE 16, arm 274 includes a base 276 secured to the blade and extending longitudinally from the edge of the blade toward the frame side member and an upright 276 for pivotal securing to linkage bar 272. It will therefore be seen that linkage means 270 is wholly within the air damper frame but allows free pivotal movement of the blades since it is positioned along the blade side edge.

The blade assembly 224 may be opened or closed 'to allow or preclude air fiow therethrough by suitable manual or automatic control means connected to linkage means 270. It will be appreciated that with parallel linkage means 270 the blades will all rotate in the same direction.

It has been found that the parallel linkage means is not satisfactory in all air damper applications since the unidirectional rotation of the blades does not necessarily provide an air volume flow proportional to the rotational position of the blades. In other words, when the blades are rotated halfway between the vertical closed position and the horizontal open position the air flow volume is not one-half the volume when the blades are fully opened. To effect a proportional relationship, an opposed opening air control damper embodiment having the novel characteristics of this invention is shown in FIGURE 19.

The components of air control damper blade assembly 224, other than linkage means 270 and the manner in which the blades are mounted relative to the adjacent blade, are identical in all respects to the blade assembly now described and like reference numerals accordingly identify like parts. It will be noted, however, that the adjacent blades are mounted so that lower blade section 230 of upper blade 226 is positioned on the same side of shelf 222 as the upper blade section 232 of lower blade 228. The reason for this construction is apparent when it is appreciated that blades 226 and 228 rotate oppositely, i.e. one clockwise and the other counter-clockwise.

Sealing between adjacent blades is performed by the engagement of the longitudinal tips of the fish tail shaped portions 252 of the blade gaskets.

Opposed linkage means 280 comprises a linkage bar 282 pivotally connected at opposite ends to arm 284 fixedly mounted on lower section 230 of blade 228 and to arm 286 fixedly mounted on the lower section 230 of blade 226. It will be seen that the line of action of linkage bar 280 crosses the center-line between adjacent blade pivot axes so that clockwise rotation of one blade causes the connected adjacent blade to rotate counterclockwise. Of course, in a blade assembly comprising more than two blades another linkage bar (not shown) may be connected from arm 284 to a like arm identically positioned on the lower section of the next adjacent blade which is in turn connected to its adjacent blade by the aforedescribed link-age elements.

While there has been shown and described the fundamental novel features of this invention as applied to the particular embodiments thereof, it will be understood that various omissions and substitutions and changes in the formand details of the device illustrated and in its operation may be made by those skilled in the art without departing from the spirit of the invention. It is the intention therefore to be limited only by the scope of the following claims and reasonable equivalents thereof.

I claim:

1. An air damper assembly comprising in combination:

(a) a rectangular frame having top, bottom and opposed side members defining a plane perpendicular to the air flow path, each member having a longirudinally extending shelf parallel to the frame plane so as to define a rectangular shelf around an air flow opening;

(b) a blade assembly including a plurality of individual longitudinally extending blades, each of said blades supported at opposite ends by pivot means fixedly secured in said frame opposed side member shelves, each of said blades having an upper and lower section and an intermediate offset section, said offset section having a center-line defining the blade pivotal axis, the length of each of said blades being greater than the opening between opposed side member shelves so that the side edge portions of said blade upper section overlap the frame opposed side memher shelves on one side thereof and the side edge portions of said blade lower section overlap the frame opposed side member shelves on the other side thereof whereby the side edge portions and the frame opposed side member shelves effect a seal when the blade assembly is in a closed position, each of said blade longitudinal edges in sealing engagement with the longitudinal edge of the adjacent blade, the upper longitudinal edge of the uppermost blade and the lower longitudinal edge of the lowermost blade overlapping the frame top and bottom shelves, respectivly, when said blade assembly is in a closed position; and,

(c) linkage means interconnecting said blades for simultaneous opening and closing of said blades com prising said blade assembly.

2. The air damper assembly set forth in claim 1 wherein (a) said frame opposed side member shelves have a plurality of spaced apart rectangular notches, and

(b) each said pivot means comprises a bearing mounted in one of said notches, the face of said bearing disposed toward said opening being recessed from the inward edge of said frame side member shelf and a shaft secured to the offset section of each blade having a journal portion rotatably supported in said bearing.

3. The pivot means set forth in claim 2 wherein said shaft includes said journal portion at one end of said shaft tapering into ahexagonal portion at the opposite end of said shaft, said hexagonal portion having an irregularly shaped slot bifurcating said hexagonal portion into two oppositely disposed gripping members for receiving therebetween said blade offset section.

4. The pivot means shaft set forth in claim 3 wherein each of said gripping members comprises in cross-section two fingers and a thumb extending in parallel from a body, said fingers and thumb being separated by indentations, and said gripping members arranged relative to one another so that one of said fingers and said thumb of one of said gripping members is positioned opposite said indentations on said other gripping member.

5. The air damper assembly set forth in claim 2 wherein:

(a) said shaft is cylindrical and includes said journal portion at one end of said shaft and a slot formed in the opposite end of said shaft, and

(b) said blade offset section has a cross-sectional shape comprising a first arcuate segment connected to the blade lower section, a laterally disposed flat segment joined to said first arcuate segment which is in turn joined to a second arcuate segment connected to said blade upper section, said arcuate segments forming opposed cincular portions engaging said cylindrical shaft and said lateral fiat segment fitted in said shaft slot.

6. The air damper assembly set forth in claim 1 wherein each said blade lower section includes a longitudinally extending trailing edge, supporting means for sealing said trailing edge with the upper section of the lower adjacent blade.

7. The air damper assembly set forth in claim 6 wherein each said blade upper section includes a longitudinally extending leading edge, supporting means for sealing said leading edge with the trailing edge sealing means of the upper adjacent blade.

8. The air damper assembly set forth in claim 7 wherein each said sealing means comprises a longitudinally extending channel formed at said edge supporting a laterally and transversely projecting longitudinally extending gasket.

9. The air damper assembly set forth in claim 6 wherein each said blade upper section includes a longitudinally extending inset portion formed therein for engaging said trailin-g edge sealing means when said blade assembly is in a closed position.

10. The air damper assembly set forth in claim 9 wherein the blade upper section includes a longitudinally extending leading edge joined to said inset portion, said leading edge including a portion angularly disposed to the plane of said blade upper section and a pin receiving circular arc formed at the free end thereof whereby the axis of said circular arc is laterally offset from the plane of said blade upper section.

11. The air damper assembly set forth in claim 10 wherein said linkage means comprises (a) a linkage bar disposed parallel to said frame side members and adjacent the side edge of each of said blades, and

(b) pins interconnecting said linkage bar and each of said blade leading edge circular arcs.

12. The air damper assembly set forth in claim 10 wherein each of said blade leading edges includes a notch formed in said pin receiving circular are extending transversely through said blade leading edge angularly disposed portion and said linkage means comprises (a) a linkage bar disposed parallel to said frame side members and positioned in each of said blade notches, and

(b) pins interconnecting said linkage bar and each of said blade leading edge circular arcs.

13. The air damper assembly set forth in claim 1 wherein the adjacent upper and lower sections of each pair of adjacent blades overlap the frame opposed side member shelves on the same side thereof and said linkage means effects simultaneous rotation of said blades in op posite directions.

14. Theair damper assembly set forth in claim 1 wherein the adjacent upper and lower sections of each pair of adjacent blades overlap the frame opposed side member shelves on opposite sides thereof and said linkage means effects simultaneous rotation of said blades in the same direction.

15. The air damper assembly set forth in claim 1 wherein said offset section of each of said blades is laterally positioned from the blade upper longitudinal edge a distance less than one-third the width of said blade whereby the blade area below said pivotal axis is substantially greater than the area above said pivotal axis.

16. The air damper assembly set forth in claim 1 additionally including means for releasably securing the plurality of blades comprising said blade assembly in any position.

References Cited UNITED STATES PATENTS 2,928,332 3/1960 Goettl et al. 98-40 2,997,939 8/1961 Snyder et al. 98-110 3,120,035 2/1964 Morris 98-110 XR 3,123,098 3/1964 Bishop 98-110 XR 3,204,548 9/1965 McCabe 98-110 XR 3,191,241 6/1965 Johnson 98-110 XR 3,301,164 l/1967 Eberhart 98-121 XR 3,313,226 4/1967 Johnson 98-121 XR ROBERT A. OLEARY, Primary Examiner.

EDWARD 1. MICHAEL, Examiner.

M. A. ANTONAKAS, Assistant Examiner. 

1. AN AIR DAMPER ASSEMBLY COMPRISING IN COMBINATION: (A) A RECTANGULAR FRAME HAVING TOP, BOTTOM AND OPPOSED SIDE MEMBERS DEFINING A PLANE PERPENDICULAR TO THE AIR FLOW PATH, EACH MEMBER HAVING A LONGITUDINALLY EXTENDING SHELF PARALLEL TO THE FRAME PLANE SO AS TO DEFINE A RECTANGULAR SHELF AROUND AN AIR FLOW OPENING; (B) A BLADE ASSEMBLY INCLUDING A PLURALITY OF INDIVIDUAL LONGITUDINALLY EXTENDING BLADES, EACH OF SAID BLADES SUPPORTED AT OPPOSITE ENDS BY PIVOT MEANS FIXEDLY SECURED IN SAID FRAME OPPOSED SIDE MEMBER SHELVES, EACH OF SAID BLADES HAVING AN UPPER AND LOWER SECTION AND AN INTERMEDIATE OFFSET SECTION, SAID OFFSET SECTION HAVING A CENTER-LINE DEFINING THE BLADE PIVOTAL AXIS, THE LENGTH OF EACH OF SAID BLADES BEING GREATER THAN THE OPENING BETWEEN OPPOSED SIDE MEMBER SHELVES SO THAT THE SIDE EDGE PORTIONS OF SAID BLADE UPPER SECTION OVERLAP THE FRAME OPPOSED SIDE MEMBER SHELVES ON ONE SIDE THEREOF AND THE SIDE EDGE PORTIONS OF SAID BLADE LOWER SECTION OVERLAP THE FRAME OPPOSED SIDE MEMBER SHELVES ON THE OTHER SIDE THEREOF WHEREBY THE SIDE EDGE PORTIONS AND THE FRAME OPPOSED SIDE MEMBER SHELVES EFFECT A SEAL WHEN THE BLADE ASSEMBLY IS IN A CLOSED POSITION, EACH OF SAID BLADE LONGITUDINAL EDGES IN SEALING ENGAGEMENT WITH THE LONGITUDINAL EDGE OF THE ADJACENT BLADE, THE UPPER LONGITUDINAL EDGE OF THE UPPERMOST BLADE AND THE LOWER LONGITUDINAL EDGE OF THE LOWERMOST BLADE OVERLAPPING THE FRAME TOP AND BOTTOM SHELVES, RESPECTIVELY, WHEN SAID BLADE ASSEMBLY IS IN A CLOSED POSITION; AND, (C) LINKAGE MEANS INTERCONNECTING SAID BLADES FOR SIMULTANEOUS OPENING AND CLOSING OF SAID BLADES COMPRISING SAID BLADE ASSEMBLY. 